Pilot oil ignition gas engine and method of operating pilot oil ignition gas engine

ABSTRACT

The gas engine of the present invention has a pilot oil fuel valve, a pilot oil pump, and first and second pipes connected to a pilot oil main pipe, for each of a plurality of combustion chambers. An operating pilot oil tank and an ignition stimulant-added pilot oil tank are connected via a switching valve to a third pipe, connected to an end of the pilot oil main pipe. Before operating stops, the pilot oil is discharged by opening an exhaust valve, and thereafter, the switching valve is switched and pilot oil which the ignition stimulant has been added to is supplied into the pipe. Consequently, the pilot oil downstream from the main pipe is replaced with the pilot oil which the ignition stimulant has been added to. Therefore, at the time of the next activation, pilot oil which the ignition stimulant has been added to is sprayed from the fuel valve, and, as a result, misfire at the time of activation is reduced, and a highly reliable engine is obtained.

BACKGROUND OF INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a structure of a gas engine forreducing the ratio of misfire generated at the time of activating apilot oil ignition type gas engine, and increasing the activationstability, and also relates to an operating method of the gas engine.

[0003] 2. Description of Related Art

[0004] Since pilot ignition type gas engines, which perform compressionignition, have higher ignition energy than conventional spark plugignition type gas engines, they can achieve a far greater increase inoutput. However, a pilot ignition oil type gas engine is also ignited bya spark plug or the like, since compression ignition is difficult at thetime of activating in a low-temperature combustion chamber. Therefore,to make the engine more economical by reducing the number of itscomponents, or to achieve smoother activation, there is a need to adjustconditions so as to enable earlier compression ignition and realizepilot oil ignition operation from the cranking time.

[0005]FIG. 1 is a cross-sectional view of the region near a cylinderhead 1 of a pilot oil ignition type gas engine proposed by the presentinventors. A spark plug 4 for activation is provided in a maincombustion chamber 2 in which a piston 3 rises and falls. Furthermore, apreparatory combustion chamber 5 for pilot oil ignition leads to themain combustion chamber 2. A pilot oil fuel valve 6 is provided insidethe preparatory combustion chamber 5. The pilot oil fuel valve 6 isconnected via a pipe 8 to a pilot oil pump 7. The pilot oil pump 7 isdriven by the driving force of the gas engine. Although not illustratedin FIG. 1, the pilot oil pump 7 is connected via a pipe to a pilot oiltank. Furthermore, although not illustrated in FIG. 1, gas fuel issupplied from a fuel supply source via a fuel supply valve to the maincombustion chamber 2.

[0006] At the time of activation, a spark is generated by the electrodeof the spark plug 4 at an appropriate timing, and the gas fuel suppliedinto the main combustion chamber 2 is ignited. The pilot oil is forcedto the pilot oil fuel valve 6 by the pilot oil pump 7 which is driven bythe engine. The pressure applied to the pilot oil increases as thenumber of rotations of the engine increases, and the pilot oil starts tospray into the preparatory combustion chamber 5 at the point where thispressure exceeds the valve-open pressure of the pilot oil fuel valve 6.Then, when the temperature inside the preparatory combustion chamber 5at the time of spraying the pilot oil has exceeded the self-ignitiontemperature of the pilot oil, the pilot oil ignition operation begins,and the spark plug 4 stops sparking.

[0007] When misfire is generated during the activation, uncombusted gasis released into the exhaust. When the ratio of generated misfireincreases, so does the density of combustion gas in the exhaust pipe,and, when the gas density reaches a flammable range, there is a dangerof sudden combustion in the exhaust pipe. Furthermore, when the ratio ofmisfire increases, the engine may fail to activate (stall).

[0008] Therefore, in a system using a gas engine, it is important toreduce misfire at the time of activation.

DISCLOSURE OF INVENTION

[0009] The invention according to a first aspect is characterized inthat, in a pilot oil ignition type gas engine having a pilot oil fuelvalve provided in a combustion chamber, an operating pilot oil tank, anda pipe section which connects the pilot oil fuel valve to the operatingpilot oil tank, the pilot oil ignition type gas engine beingcompression-ignited by pilot oil sprayed from the pilot oil fuel valveinto the combustion chamber, an ignition stimulant-added pilot oil tankis connected to the pipe section via a pilot oil switching valve.

[0010] Furthermore, the invention according to a second aspect ischaracterized in that, in a pilot oil ignition type gas engine having aplurality of pilot oil combustion valves provided in a plurality ofcombustion chambers, a plurality of pilot oil pumps provided to each ofthe pilot oil combustion valves, a plurality of first pipes whichconnect the pilot oil combustion valves with the corresponding pilot oilpumps, a pilot oil main pipe, a plurality of second pipes which connectthe pilot oil pumps to the pilot oil main pipe, an operating pilot oiltank, and a pipe which connects an end of the pilot oil main pipe to theoperating pilot oil tank, a pilot oil exhaust valve is provided atanother end of the pilot oil main pipe, and an ignition stimulant-addedpilot oil tank being connected to the third pipe via a pilot oilswitching valve.

[0011] Furthermore, the invention according to a third aspect ischaracterized in that, in a pilot oil ignition type gas engine having apilot oil fuel valve provided in a combustion chamber, an operatingpilot oil tank, and a pipe which connects the pilot oil fuel valve tothe operating pilot oil tank, the pilot oil ignition type gas enginebeing compression-ignited by pilot oil sprayed from the pilot oil fuelvalve into the combustion chamber, an ignition stimulant-added pilot oiltank is connected to the pipe via a flow adjusting valve.

[0012] Furthermore, the invention according to a fourth aspect ischaracterized in that, in a pilot oil ignition type gas engine having aplurality of pilot oil combustion valves provided in a plurality ofcombustion chambers, a plurality of pilot oil pumps provided to each ofthe pilot oil combustion valves, a plurality of first pipes whichconnect the pilot oil combustion valves with the corresponding pilot oilpumps, a pilot oil main pipe, a plurality of second pipes which connectthe pilot oil pumps to the pilot oil main pipe, an operating pilot oiltank, and a pipe which connects an end of the pilot oil main pipe to theoperating pilot oil tank, a pilot oil exhaust valve is provided atanother end of the pilot oil main pipe, and an ignition stimulant-addedpilot oil tank is connected to the third pipe via a flow adjustingvalve.

[0013] In the pilot oil ignition type gas engine as described in thesecond and fourth aspects of the invention, it is preferable that thepilot oil exhaust valve and the operating pilot oil tank are connectedby a fourth pipe, and that the pilot oil discharged from the pilot oilexhaust valve is returned to the operating pilot oil tank.

[0014] Furthermore, in the pilot oil ignition type gas engine asdescribed in the third and fourth aspects of the invention, it ispreferable that the pilot oil exhaust valve and the operating pilot oiltank are connected by a fourth pipe, and that the pilot oil dischargedfrom the pilot oil exhaust valve is returned to the operating pilot oiltank.

[0015] Furthermore, in the pilot oil ignition type gas engine asdescribed in the third and fourth aspects of the invention, it ispreferable that a pressure pump for mixing an ignition stimulant intothe pilot oil inside the pipe (or the third pipe) is provided betweenthe ignition stimulant tank and the flow adjusting valve.

[0016] Moreover, in the pilot oil ignition type gas engine as describedin the third and fourth aspects of the invention, it is preferable thatthe head height to the ignition stimulant tank is higher than the headheight to the operating pilot oil tank.

[0017] Furthermore, the invention according to a fifth aspect providesan operating method for a pilot oil ignition type gas engine, which iscompression-ignited by pilot oil sprayed from a pilot oil fuel valveinto a combustion chamber, connected to an operating pilot oil tank, thepilot oil which is sprayed into the combustion chamber at the time ofactivation comprising ignition stimulant-added pilot oil.

[0018] In this case, for example, before operating stops, at least partof the pilot oil inside the pipe and the pilot oil fuel valve from theoperating pilot oil tank to the pilot oil fuel valve comprises pilot oilwhich ignition stimulant has been added to, so that pilot oil whichignition stimulant has been added to is sprayed into the combustionchamber at the time of the next activation.

BRIEF DESCRIPTION OF DRAWINGS

[0019]FIG. 1 is a cross-sectional view of the region near a cylinderhead of a pilot oil ignition type gas engine proposed by the presentinventors.

[0020]FIG. 2 is a schematic view illustrating the constitution of afirst example of the present invention.

[0021]FIG. 3 is a time chart showing an operating method of a firstexample of a gas engine of the present invention.

[0022]FIG. 4 is a diagram showing the relationship between the rate ofmisfire and the number of engine rotations, in order to compare theeffects of the first example of the gas engine of the present invention(solid line) with the gas engine proposed by the present inventors priorto the present application.

[0023]FIG. 5 is a schematic view illustrating the constitution of asecond example of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0024] A first example of a preferred embodiment of the presentinvention will be explained with reference to FIGS. 1 to 4.

[0025] The constitution of the components around the main combustionchamber of the gas chamber in this example is the same as that shown inFIG. 1. That is, in a cylinder head 1, a preparatory combustion chamber5 leads to a main combustion chamber 2 in which a piston 3 rises andfalls, and a pilot oil fuel valve 6 is provided inside the preparatorycombustion chamber 5. The pilot oil fuel valve 6 is connected via afirst pipe 8 to a pilot oil pump 7, which is driven by the driving forceof the gas engine. Furthermore, as shown in FIG. 2, the pilot oil pump 7is connected via a second pipe 9 to a pilot oil main valve 10.

[0026]FIGS. 1 and 2 show only one pair comprising the pilot oil fuelvalve 6 and the pilot oil pump 7, but since the gas engine of thisexample has multiple cylinders, the pilot oil fuel valve 6, the pilotoil pump 7, and the first and second pipes 8 and 9, are provided in eachcylinder.

[0027] As shown in FIG. 2, the second pipe 9 connects to a common pilotoil main pipe 10. Although not shown in detail in FIG. 2, a plurality ofsecond pipes 9 correspond to a plurality of pilot oil fuel valves 6, andare connected to the pilot oil main valve 10 at predetermined intervals.Further, an operating pilot oil tank 12 is connected to one end of thepilot oil main valve 10. The pilot oil tank 12 stores pilot oil which issprayed into the combustion chamber for pilot oil ignition bycompression ignition.

[0028] Oil having an ignition point of between 40° C. and 70° C., and acetane number and cetane index of between 40 and 60, can be used as thepilot oil. Specific examples are light oil or fuel oil A. The preferableproperties of this light oil are that it should have an ignition pointof greater than 50° C., a flow point of less than −2.5° C., satisfying aJIS K 2070 (the residual carbon element of residual oil distilled to 10%being less than 0.1 wt % according to Condrason's method), the cetanenumber and cetane index of greater than 50, a kinematic viscocity ofgreater than 2.7 cSt at 30 C, and an orpiment element of less than 0.5wt %. Furthermore, the preferable properties of the fuel oil A are thatit should have an ignition point of greater than 60 C, a flow point ofless than 6 C, satisfying a JIS K 2070 (the residual carbon element ofresidual oil distilled to 10% being less than 1.3 wt % according toCondrason's method), the cetane number and cetane index of greater than45, a kinematic viscocity of less than 5.5 cSt at 50 C, and an orpimentelement of less than 1.0 wt %.

[0029] An ignition stimulant-added pilot oil tank 14 is connected midwayalong a third pipe 11. The ignition stimulant-added pilot oil tank 14stores pilot oil which an ignition stimulant has been added to, for useat the time of activation. By using the pilot oil which an ignitionstimulant has been added to, the pilot oil ignition operation can beperformed earlier.

[0030] The ignition stimulant should be one which can increase thecetane number of the pilot oil and safely stimulate ignition withoutcausing problems to the engine; the cetane number of the pilot oilshould be increased by 5% to 25% as a result of adding the ignitionstimulant. For example, alkyl nitrate, alkylene nitrate, amine nitrate,and the like, can be used as the ignition stimulant; more specificexamples are 2-ethyl hexyl nitrate or 2,2-dinitro propane. Furthermore,any type of commercially available additive which is added to diesel oilused as diesel engine fuel, and which contains at least one of the abovesubstances, can be used as the ignition stimulant.

[0031] Furthermore, a pilot oil exhaust valve 15 is provided at theother end of the pilot oil main valve 10, and faces upwards. Before theend of the operation of the engine, this valve is opened to dischargethe pilot oil in the pipe, and the ignition stimulant-added pilot oil isfed from the ignition stimulant-added pilot oil tank 14 into the pipe,thereby replacing the pilot oil with the ignition stimulant-added pilotoil. Incidentally, although illustrated in the diagrams, the exit of thepilot oil exhaust valve 15 may be connected to the pilot oil tank 12 bya fourth pipe, so as to return the pilot oil discharged from the pilotoil main valve 10 to the pilot oil tank 12.

[0032] A method for operating the gas engine having the constitutiondescribed above will explained based on the time chart shown in FIG. 3.

[0033] During rated operation of the gas engine, the pilot oil tank 12is joined to the third pipe 11, and the ignition stimulant-added pilotoil tank 14 is cut off from the third pipe 11. Therefore, only regularpilot oil is supplied through the pipe and sprayed from the pilot oilfuel valve 6 during the pilot oil ignition operation.

[0034] The following control is carried out to stop the gas engine whileit is operating. Firstly, before stopping the gas engine, as shown inFIG. 3 by “use additive line” before “stop” in the “number of enginerotations”, the pilot oil switching valve 13 is switched so that theignition stimulant-added pilot oil tank 14 becomes connected to thethird pipe 11, cutting off the pilot oil tank 12 from the third pipe 11.Then, the pilot oil exhaust valve 15 of the pilot oil main valve 10 isopened, and more pilot oil than the amount as far as the other end ofthe pilot oil main valve 10 is discharged from the pilot oil switchingvalve 13.

[0035] In this case, the amount of pilot oil to be discharged isexpressed by the following equation (1).

Amount contained in third pipe 11 [L]+Amount contained in pilot oil mainvalve 10 [L]<Amount of discharged pilot oil [L]  (1)

[0036] As a result, the pilot oil from the pilot oil switching valve 13to the other end of the pilot oil main valve 10 is replaced by theignition stimulant-added pilot oil. Then, by continuing to operate thegas engine by a fixed period of time, the pilot oil in the second pipe9, the pilot oil pump 7, the pipe 8, and the pilot oil fuel valve 6,which are downstream from the pilot oil main valve 10, is replaced bythe ignition stimulant-added pilot oil. Thereafter, the engine isstopped.

[0037] In this case, the time taken to operate the gas engine in orderto replace the oil downstream from the pilot oil main valve 10 with theignition stimulant-added pilot oil is expressed by the followingequation (2).

{(Amount contained in second pipe 9+Amount contained in pilot oil pump7+Amount contained in pipe 8+Amount contained in pilot oil fuel valve 6)[L]×Number of cylinders}÷Amount of pilot oil consumed [L/min]<Operatingtime [min]  (2)

[0038] Furthermore, the amount contained in the ignition stimulant-addedpilot oil tank 14 is expressed by the following equation (3).

Amount contained in third pipe 11+Amount contained in pilot oil mainvalve

[0039]10+(Amount contained in second pipe 9+Amount contained in pilotoil pump 7+Amount contained in pipe 8+Amount contained in pilot oil fuelvalve 6) [L]×Number of cylinders+Amount of pilot oil needed at the timeof activation [L]<Amount contained in ignition stimulant-added pilot oiltank 14 [L]  (3)

[0040] As a result of the above control, the sections of the stopped gasengine from the pilot oil switching valve 13 as far as the pilot oilfuel valve 6 become filled with the ignition stimulant-added pilot oil,and the ignition stimulant-added pilot oil tank 14 is connected to thethird pipe 11. At the time of activating the gas engine, as shown inFIG. 3 by “use additive line” from a zero “number of engine rotations”to “activate” and “rated operation”, the ignition stimulant-added pilotoil tank 14 remains connected to the third pipe 11 until the gas enginereaches rated operation; when the gas engine enters rated operation, thepilot oil switching valve 13 is switched, and the third pipe 11 isconnected to the pilot oil tank 12.

[0041] The gas engine is activated by sparking the spark plug 4. Asshown by “spark ON” in FIG. 3, from “activate” in “number of enginerotations” to “rated operation”, the spark of the spark plug 4 continuesuntil the gas engine reaches rated operation.

[0042] As the number of engine rotations increases, so does the pressureapplied to the ignition stimulant-added pilot oil by the pilot oil pump7. Then, as the number of engine rotations further increases, when thepressure applied to the ignition stimulant-added pilot oil has exceededthe valve-open pressure of the pilot oil fuel valve 6, the ignitionstimulant-added pilot oil starts to spray. As shown in FIG. 3 by thetiming of “pilot oil spray”, the ignition stimulant-added pilot oilstarts to spray before the gas engine reaches rated operation. Then, atthe point where the compression temperature in the preparatorycombustion chamber 5 at the time of spraying the pilot oil exceeds theself-ignition temperature of the pilot oil, the pilot oil ignitionoperation starts, and the spark of the spark plug 4 stops. For example,when the number of rotations of the gas engine has reached the ratednumber of rotations, the pilot oil ignition operation starts, and thespark of the spark plug 4 stops. Since the ignition stimulant has beenadded to the pilot oil used in the pilot oil ignition operation, misfireis unlikely to occur.

[0043] As shown in FIG. 3 by “use additive line” after the “ratedoperation” of “number of engine rotations”, when the gas engine reachesrated operation, the pilot oil switching valve 13 is switched, cuttingoff the ignition stimulant-added pilot oil tank 14 from the third pipe11, so that the third pipe 11 is connected to the pilot oil tank 12.Therefore, during rated operation, the gas engine is ignited by regularpilot oil supplied from the pilot oil tank 12.

[0044] As described above, at the time of activating the gas engine,regular pilot oil is replaced by ignition stimulant-added pilot oil, andconsequently, the shift to pilot oil ignition from activation by thespark plug 4 is performed smoothly without generating misfire. Moreover,since the number of engine rotations which is unlikely to generatemisfire at the time of activation can be reduced to less than in aconventional gas engine, activation is more dependable and smoother,increasing the reliability of the gas engine. Further, in a constitutionwhere the exit of the pilot oil exhaust valve 15 is connected by afourth pipe to the pilot oil tank 12, the pilot oil which is dischargedfrom the pilot oil main valve 10 can be returned to the pilot oil tank12, thereby avoiding wasteful energy consumption. In this case, evenwhen a small amount of mixed oil returns to the tank, no problems arisein the operation of the engine.

[0045] A specific example of effects of the gas engine having theconstitution described above, and an operating method thereof, will beexplained with reference to FIG. 4.

[0046]FIG. 4 shows the misfire rates at the time of activation of asix-cylinder gas engine having a bore of 220 mm and a stroke of 300 mm(shown by the broken line in FIG. 4), which was proposed by the presentinventors prior to the present invention, and the gas engine of thepresent invention having a bore of 220 mm and a stroke of 300 mm (shownby the solid line in FIG. 4). The misfire rate represents the percentageof cycles in which the P mi (indicated mean effective pressure shown inFIG. 4) was below zero, out of eighteen continuous cycles.

[0047] In the gas engine prior to the present invention (shown by thebroken line in FIG. 4), the misfire rate at the time of activationdecreases as the number of rotations of the engine increases, andbecomes zero (no misfire) at 950 rpm.

[0048] In contrast, in the gas engine of the present invention (shown bythe solid line in FIG. 4), which uses LZ8090 manufactured by theLubrizol Performance Products Company as the ignition stimulant, mixedin fuel oil A to a percentage of 1%, although the misfire immediatelyafter activation is the same as that in the gas engine prior to thepresent invention, the misfire rapidly decreases as the number ofrotations of the engine increases, and becomes zero when the number ofengine rotations is 450 rpm; this is lower than in the gas engine priorto the present invention.

[0049] By applying the constitution and method which enable the pilotoil to be replaced with ignition stimulant-added pilot oil at the timeof activating the pilot oil ignition gas engine, the misfire rate andnumber of rotations which misfire ceases to be generated at the time ofactivating the pilot oil ignition gas engine become less than inconventional engines. Therefore, the engine can be activated reliablyand smoothly.

[0050] Incidentally, the abovementioned effects of the gas engineaccording to the present invention are obtained in the case of asix-cylinder gas engine having a cylinder diameter of 220 mm, but thepresent invention can be applied in pilot oil ignition type gas engineshaving other cylinder diameters and numbers of cylinders, and can obtaincorresponding effects.

[0051] A second example of an embodiment of the present invention willbe explained with reference to FIG. 5.

[0052] As shown in FIG. 5, the gas engine of this example ischaracterized in that, instead of connecting the ignitionstimulant-added pilot oil tank 14 via the pilot oil switching oil valve13 to the pipe as in the first example, an ignition stimulant tank(ignition stimulant source-holding tank) 16 is connected to the thirdpipe 11 via a flow adjusting valve 17.

[0053] The amount contained in the ignition stimulant tank 16 isexpressed by the following equation (4).

{Amount contained in third pipe 11 [L]+Amount contained in pilot oilmain

[0054] valve 10 [L]+(Amount contained in second pipe 9+Amount containedin pilot oil pump 7+Amount contained in pipe 8+Amount contained in pilotoil fuel valve 6) [L]×Number of cylinders+Amount of pilot oil needed atthe time of activation [L]×Mixing rate [%]/100 <Amount contained inignition stimulant tank 16 [L]  (4)

[0055] Furthermore, to mix the ignition stimulant from the ignitionstimulant tank 16 into the pilot oil in the third pipe 11, a pressurepump 18 is provided on the pipe which connects the ignition stimulanttank 16 to the j17. For the same purpose, instead of, or in addition to,providing the pressure pump 18, the head height to the ignitionstimulant tank 16 may acceptably be made higher than the head height tothe pilot oil tank 12.

[0056] The constitution is otherwise identical to that of the firstexample, and so is its operating method. Furthermore, this exampleobtains practically the same effects as the first example.

1. A pilot oil ignition type gas engine having a pilot oil fuel valveprovided in a combustion chamber, an operating pilot oil tank, and apipe section which connects the pilot oil fuel valve to the operatingpilot oil tank, the pilot oil ignition type gas engine beingcompression-ignited by pilot oil sprayed from the pilot oil fuel valveinto the combustion chamber; wherein an ignition stimulant-added pilotoil tank being connected to the pipe section via a pilot oil switchingvalve.
 2. A pilot oil ignition type gas engine having a plurality ofpilot oil combustion valves provided in a plurality of combustionchambers, a plurality of pilot oil pumps provided to each of the pilotoil combustion valves, a plurality of first pipes which connect thepilot oil combustion valves with the corresponding pilot oil pumps, apilot oil main pipe, a plurality of second pipes which connect the pilotoil pumps to the pilot oil main pipe, an operating pilot oil tank, and apipe which connects an end of the pilot oil main pipe to the operatingpilot oil tank; wherein a pilot oil exhaust valve being provided atanother end of the pilot oil main pipe, and an ignition stimulant-addedpilot oil tank being connected to the third pipe via a pilot oilswitching valve.
 3. A pilot oil ignition type gas engine having a pilotoil fuel valve provided in a combustion chamber, an operating pilot oiltank, and a pipe which connects the pilot oil fuel valve to theoperating pilot oil tank, the pilot oil ignition type gas engine beingcompression-ignited by pilot oil sprayed from the pilot oil fuel valveinto the combustion chamber; wherein an ignition stimulant-added pilotoil tank being connected to the pipe via a flow adjusting valve.
 4. Apilot oil ignition type gas engine having a plurality of pilot oilcombustion valves provided in a plurality of combustion chambers, aplurality of pilot oil pumps provided to each of the pilot oilcombustion valves, a plurality of first pipes which connect the pilotoil combustion valves with the corresponding pilot oil pumps, a pilotoil main pipe, a plurality of second pipes which connect the pilot oilpumps to the pilot oil main pipe, an operating pilot oil tank, and apipe which connects an end of the pilot oil main pipe to the operatingpilot oil tank; wherein a pilot oil exhaust valve being provided atanother end of the pilot oil main pipe, and an ignition stimulant-addedpilot oil tank being connected to the third pipe via a flow adjustingvalve.
 5. The pilot oil ignition type gas engine as described in claim2, wherein the pilot oil exhaust valve and the operating pilot oil tankare connected by a fourth pipe, and pilot oil discharged from the pilotoil exhaust valve is returned to the operating pilot oil tank.
 6. Thepilot oil ignition type gas engine as described in claim 4, wherein thepilot oil exhaust valve and the operating pilot oil tank are connectedby a fourth pipe, and pilot oil discharged from the pilot oil exhaustvalve is returned to the operating pilot oil tank.
 7. The pilot oilignition type gas engine as described in claim 3, wherein a pressurepump for mixing an ignition stimulant into the pilot oil inside the pipeis provided between the ignition stimulant tank and the flow adjustingvalve.
 8. The pilot oil ignition type gas engine as described in claim4, wherein a pressure pump for mixing an ignition stimulant into thepilot oil inside the pipe is provided between the ignition stimulanttank and the flow adjusting valve.
 9. The pilot oil ignition type gasengine as described in claim 3, wherein the head height to the ignitionstimulant tank is higher than the head height to the operating pilot oiltank.
 10. The pilot oil ignition type gas engine as described in claim4, wherein the head height to the ignition stimulant tank is higher thanthe head height to the operating pilot oil tank.
 11. An operating methodfor a pilot oil ignition type gas engine which is compression-ignited bypilot oil sprayed from a pilot oil fuel valve into a combustion chamber,which is connected to an operating pilot oil tank, wherein the pilot oilwhich is sprayed into the combustion chamber at the time of activationcomprising ignition stimulant-added pilot oil.
 12. The operating methodfor a pilot oil ignition type gas engine as described in claim 11,wherein, before operating stops, at least part of the pilot oil insidethe pipe and the pilot oil fuel valve from the operating pilot oil tankto the pilot oil fuel valve comprises pilot oil which ignition stimulanthas been added to, so that pilot oil which ignition stimulant has beenadded to is sprayed into the combustion chamber at the time of the nextactivation.